Flame-retardant polycarbonate resin composition and molded article thereof

ABSTRACT

A flame-retardant polycarbonate resin composition which exhibits excellent flame-retarding property and retention of the antistatic property for a long time. It comprises (A) a polycarbonate resin, (B) an aromatic vinyl resin having an acid salt group and (C) a silicone compound having a reactive group.

TECHNICAL FIELD

The present invention relates to a flame-retardant polycarbonate resincomposition and a molded product thereof More particularly, the presentinvention relates to a flame-retardant polycarbonate resin compositionexhibiting an excellent flame-retarding property and retention of theantistatic property for a long time.

BACKGROUND ART

Polycarbonate resins are widely used in the various fields such as theelectric or electronic apparatus fields for office automationapparatuses, information and communication apparatuses and householdelectric apparatuses and the like, the automobile field, the lightingapparatus field and the building field due to the excellent impactresistance, heat resistance and dimensional stability. Although thepolycarbonate resin has the self-extinguishing property by itself, it isdesired that the flame-retarding property is enhanced to further improvethe safety when the resin is used as a raw material for electric andelectronic apparatuses such as office automation apparatuses, members ofautomobiles and members of lighting apparatuses.

As the method for improving the flame-retarding property of thepolycarbonate resin, halogen-based flame retardants such as halogenatedbisphenol A and halogenated polycarbonate oligomers have been used incombination with an auxiliary flame retardant such as antimony oxide dueto the excellent efficiency of flame retardation. However, in recentyears, a method for flame retardation using a flame retardant containingno halogens is required from the standpoint of the safety and the greateffect of the flame retardants containing a halogen on the environmentduring incineration. Since the excellent flame-retarding property andthe effect as a plasticizer are exhibited simultaneously when an organicphosphorus-based flame retardant, in particular, an organic phosphoricacid ester compound, is used as the flame retardant containing nohalogens, flame-retardant polycarbonate resin compositions using theorganic phosphoric acid ester compound are proposed.

However, it is necessary that the organic phosphoric acid ester compoundbe used in a relatively great amount for flame retardation of apolycarbonate resin with the organic phosphoric acid ester compound. Toproduce a thinner molded article having a great size, it is necessarythat the molding temperature be elevated since the polycarbonate resinrequires a high temperature for molding and has a great melt viscosity.Therefore, the organic phosphoric acid ester compound is not alwayssatisfactory from the standpoint of the environment of molding and theappearance of the product due to drawbacks such as attachment of thecompound to a mold and generation of gases during the working althoughthe compound contributes to exhibiting the flame-retarding property. Themolded product obtained from the flame-retardant polycarbonate resincomposition using the organic phosphoric acid ester compound has adrawback in that a decrease in impact strength and discoloration takeplace after exposure to a high temperature or to a high temperature anda high humidity.

In Japanese Patent Application Laid-Open No. Showa 50(1975)-98546, toovercome the above problems, it is proposed that a polycarbonate resinis made flame retardant by using a small amount of a metal salt of apolymeric aromatic sulfonic acid such as the sodium salt of apolystyrenesulfonic acid. However, when polystyrene is sulfonated inaccordance with a conventional process and neutralized with sodiumhydroxide and a polycarbonate is made flame retardant with the obtainedsodium polystyrenesulfonate, a drawback arises in that the appearance ofthe product becomes poor due to poor dispersion of sodiumpolystyrenesulfonate although the excellent flame-retarding property canbe obtained.

For a flame-retardant polycarbonate resin composition, it is alsorequired that a material for molding which is made flame retardant whilethe excellent physical properties proper to the polycarbonate resin isretained be developed. To satisfy the requirement, for example, aflame-retardant polycarbonate resin composition obtained by adding anorganic alkali metal salt or an organic alkaline earth metal salt and anorganopolysiloxane to a polycarbonate resin is proposed in JapanesePatent Application Laid-Open No. Heisei 8(1996)-176425. However, thiscomposition has a drawback in that dusts are easily attached to thesurface of the product obtained by molding the flame-retardantpolycarbonate resin composition.

As described above, the development of a flame-retardant polycarbonateresin composition which provides an article exhibiting excellentflame-retarding property and retention of the antistatic property toprevent the attachment of dusts, has been desired.

The present invention has an object of providing a flame-retardantpolycarbonate resin composition which provides an article exhibitingexcellent flame-retarding property and retention of the antistaticproperty to prevent the attachment of dusts and a molded articlethereof.

DISCLOSURE OF THE INVENTION

As the result of extensive studies by the present inventors to overcomethe above problems, it was found that the above object could be achievedwith a flame-retardant polycarbonate resin composition comprising apolycarbonate resin, an aromatic vinyl resin having an acid salt groupand a silicone compound having a reactive group in specific relativeamounts. The present invention has been completed based on thisknowledge.

The present invention can be summarized as:

-   [1] A flame-retardant polycarbonate resin composition which    comprises 90 to 99.9% by mass of a polycarbonate resin as component    (A), 0.05 to 5% by mass of an aromatic vinyl resin having an acid    salt group as component (B) and 0.05 to 5% by mass of a silicone    compound having a reactive group as component (C);-   [2] A flame-retardant polycarbonate resin composition as described    in [1], wherein the polycarbonate resin of component (A) is a    polycarbonate copolymer resin having a structural unit derived from    an organosiloxane;-   [3] A flame-retardant polycarbonate resin composition as described    in any one of [1] and [2], wherein the aromatic vinyl resin having    an acid salt group of component (B) is a metal salt of a    polystyrenesulfonic acid;-   [4] A flame-retardant polycarbonate resin composition as described    in any one of [1] to [3], wherein the silicone compound having a    reactive group of component (C) is a silicone compound having a    reactive group and phenyl group;-   [5] A flame-retardant polycarbonate resin composition as described    in any one of [1] to [4], wherein the silicone compound having a    reactive group of component (C) is a silicone compound having at    least one reactive group selected from a group consisting of alkoxyl    group, hydroxyl group, epoxy group and vinyl group;-   [6] A flame-retardant polycarbonate resin composition as described    in any one of [1] to [5], which further comprises at least one    stabilizer selected from a group consisting of antioxidants and    ultraviolet light absorbents as component (D);-   [7] A molded article prepared by molding a flame-retardant    polycarbonate resin composition described in any one of [1] to [6];-   [8] A molded article as described in [7], which is a member of an    electric or electronic apparatus, a member of an automobile or a    member of a lighting apparatus; and-   [9] A molded article as described [7], which is a lens of a head    lamp of an automobile.

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

The most preferred embodiment to carry out the invention will bedescribed in the following.

The flame-retardant polycarbonate resin composition of the presentinvention comprises 90 to 99.9% by mass of a polycarbonate resin ascomponent (A), 0.05 to 5% by mass of an aromatic vinyl resin having anacid salt group as component (B) and 0.05 to 5% by mass of a siliconecompound having a reactive group as component (C). To the basicflame-retardant polycarbonate resin composition comprising components(A), (B) and (C) in specific relative amounts, at least one stabilizerselected from a group consisting of antioxidants and ultraviolet lightabsorbents as component (D) may be added, where necessary.

The polycarbonate resin of component (A), the aromatic vinyl resinhaving an acid salt group of component (B), the silicone compound havinga reactive group of component (C) and the stabilizer of component (D)will be described in detail in the following.

(A) Polycarbonate Resin

The polycarbonate resin used as component (A) of the raw materials ofthe flame-retardant polycarbonate resin composition of the presentinvention is not particularly limited and polycarbonate resins havingvarious structural units can be used. In general, aromaticpolycarbonates produced by the reaction of dihydric phenols andcarbonate precursors can be used. In other words, products obtained bythe reaction of dihydric phenols and carbonate precursors in accordancewith the solution process or the melt process can be used.

Examples of the dihydric phenol include 4,4′-dihydroxybiphenyl,bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane,2,2-bis(3-methyl-4-hydroxyphenyl)propane,2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)-cyclohexane, bis(4-hydroxyphenyl) ether,bis(4-hydroxyphenyl) sulfide, bis(4-hydroxyphenyl) sulfone,bis(4-hydroxyphenyl) sulfoxide, bis(4-hydroxyphenyl) ketone,hydroquinone, resorcinol and catechol. Among these dihydric phenols,bis(hydroxyphenyl)alkanes are preferable and compounds obtained by using2,2-bis(4-hydroxyphenyl)propane as the main material are morepreferable.

Examples of the carbonate precursor include carbonyl halides, carbonylesters and haloformates. Specific examples of the carbonate precursorinclude phosgene, dihaloformates of dihydric phenols, diphenylcarbonate, dimethyl carbonate and diethyl carbonate.

The molecular structure of the polymer chain of the polycarbonate resinmay be linear or branched. Examples of the branching agent used forintroducing the branched molecular structure include1,1,1-tris(4-hydroxyphenyl)ethane,α,α′,α″-tris(4-hydroxyphenyl)-1,3,5-triisopropyl-benzene,phloroglucinol, trimellitic acid and isatin bis(o-cresol). As themolecular weight modifier, phenol, p-t-butylphenol, p-t-octylphenol andp-cumylphenol can be used.

The polycarbonate resin used in the present invention may be ahomopolymer produced by using the dihydric phenol described above alone,a copolymer having the structural unit of a polycarbonate and thestructure unit of a polyorganosiloxane or a resin composition comprisingthe above homopolymer and the above copolymer. The polycarbonate resinmay also be a polyester-polycarbonate resin obtained by polymerizationof a polycarbonate in the presence of an ester precursor such as adibasic carboxylic acid which is, for example, terephthalic acid and aderivative of the dibasic carboxylic acid forming an ester. A resincomposition obtained by melt mixing polycarbonate resins having variousstructural units may be used. As the polycarbonate resin used ascomponent (A) in the present invention, a polycarbonate resinsubstantially comprising no halogen atoms in the structural unit thereofis preferable.

It is preferable that the polycarbonate resin used as component (A) hasa viscosity-average molecular weight in the range of 10,000 to 100,000.When the viscosity-average molecular weight is smaller than 10,000, thethermal and mechanical properties of the obtained resin composition arenot sufficient. When the viscosity-average molecular weight exceeds100,000, workability in molding the obtained resin composition becomespoor. It is more preferable that the viscosity-average molecular weightof the polycarbonate resin is in the range of 11,000 to 40,000 and mostpreferably in the range of 12,000 to 30,000.

(B) Aromatic Vinyl Resin Having an Acid Salt Group

As the aromatic vinyl resin having an acid salt group used as component(B) of the raw materials of the flame-retardant polycarbonate resincomposition of the present invention, aromatic vinyl resins having astructure in which some of hydrogen atoms on the aromatic ring in thepolymer chain of the aromatic vinyl resin are substituted with an acidsalt group are preferable. As the aromatic vinyl resin, aromatic vinylresins having at least a structural unit derived from styrene in thepolymer chain such as polystyrene, polystyrene modified with rubber,styrene-acrylonitrile copolymers and acrylonitrile-butadiene-styrenecopolymer resins can be used. Among these resins, polystyrene resins arepreferable.

Examples of the acid salt group substituting the hydrogen atom on thearomatic ring in the aromatic vinyl resin include alkali metal saltgroups, alkaline earth metal salt groups and ammonium salt groups ofsulfonic acid, boric acid and phosphoric acid. The fraction of thehydrogen atoms substituted with the acid salt group among the entirehydrogen atoms is not particularly limited and can be suitably selectedin the range of 10 to 100%.

As the polystyrene resin having an acid salt group which is preferableas the aromatic vinyl resin having an acid salt group, polystyreneresins having an acid salt group represented by the following generalformula (1):

wherein X represents an acid salt group, Y represents hydrogen atom or ahydrocarbon group having 1 to 10 carbon atoms, m represents an integerof 1 to 5, n represents the mole fraction of the structural unit derivedfrom styrene substituted with the acid salt group, and 0<n≦1; arepreferable.

As the acid salt group represented by X in general formula (1), saltgroups of sulfonic acid, boric acid and phosphoric acid are preferableand alkali metal salt groups such as sodium salts and potassium salts,alkaline earth metal salt groups such as the magnesium salts and calciumsalts, aluminum salts, zinc salts, tin salts and ammonium salts of theabove acids are more preferable. It is preferable that Y in generalformula (1) represents hydrogen atom and that Y represents methyl groupwhen Y represents a hydrocarbon group.

As for the process for producing the aromatic vinyl resin having an acidsalt group of component (B), the resin can be produced in accordancewith the process in which an aromatic vinyl monomer having sulfonic acidgroup or the like used as the monomer is homopolymerized orcopolymerized with other copolymerizable monomers and the obtainedproduct is neutralized with a basic substance. The above resin can beproduced also in accordance with the process in which an aromatic vinylpolymer, an aromatic vinyl copolymer or a mixture of the polymer and thecopolymer is sulfonated and the obtained product is neutralized with abasic substance. When the polymer, the copolymer or a mixture thereof issulfonated and the resultant product is neutralized with a basicsubstance, for example, the aromatic vinyl resin can be obtained byadding anhydrous sulfuric acid to a solution of polystyrene resin in1,2-dichloroethane to produce a polystyrenesulfonic acid by thereaction, neutralizing the obtained polystyrenesulfonic acid with abasic substance such as sodium hydroxide and potassium hydroxide, andpurifying the resultant product.

It is preferable that the aromatic vinyl resin having an acid salt groupof component (B) has a content of inorganic metal salts decreased toless than 5% by mass and preferably less than 3% by mass based on theamount of the aromatic vinyl resin having an acid salt group. When theproduct obtained by sulfonation of the aromatic vinyl resin such aspolystyrene resin is neutralized with sodium hydroxide and is notsubjected to any further treatments, sodium sulfate formed as abyproduct is left remaining in sodium polystyrenesulfonate. When thecontent of sodium sulfate exceeds 5% by mass, the mechanical, thermaland electrical properties of the flame-retardant polycarbonate resincomposition and the appearance of the molded article deteriorate. Sodiumpolystyrene-sulfonate can be purified by recrystallization using asolvent, separating sodium sulfate formed as a byproduct by filtrationor by a treatment with an ion exchange resin, a chelating agent or anadsorbent.

It is preferable that the aromatic vinyl resin having an acid salt groupof component (B) has a weight-average molecular weight in the range of1,000 to 300,000. When the weight-average molecular weight of thearomatic vinyl resin having an acid salt group is smaller than 1,000,physical properties of the resin composition obtained by using thisresin deteriorate. When the weight-average molecular weight of thearomatic vinyl resin having an acid salt group exceeds 300,000, fluidityof the resin composition obtained by using this resin as a componentbecomes poor and the productivity decreases.

(C) Silicone Compound Having a Reactive Group

As component (C) of the raw materials of the flame-retardantpolycarbonate resin composition of the present invention, a siliconecompound having a reactive group is used. When a flame-retardantpolycarbonate resin composition comprises a silicone compound having noreactive group as component (C), the transparency which is the excellentproperty of the polycarbonate resin cannot be retained. As the siliconecompound having a reactive group, a silicone compound having at leastone reactive group selected from the group consisting of alkoxyl group,hydroxyl group, epoxy group and vinyl group is preferable.

It is preferable that the silicone compound has a refractive index inthe range of 1.45 to 1.55. When a silicone compound having therefractive index in the above range and having the reactive group isused as component (C), the transparency of the flame-retardantpolycarbonate resin composition is improved and the flame-retardantpolycarbonate resin composition highly useful as the raw material for amolded article to which particularly excellent transparency is requiredcan be obtained.

As the silicone compound used as component (C), a silicone compoundhaving a structure in which phenyl group is bonded to the silicon atomin the main chain of the molecule is more preferable since theflame-retardant resin composition comprising the above silicone compoundas component (C) retains the excellent properties of the polycarbonateresin. Examples of the above compound include silicone compounds havingthe polymethylphenylsiloxane structure or the polydiphenyl-siloxanestructure in the main chain and at least one reactive group selectedfrom the group consisting of alkoxyl group, hydroxyl group, epoxy groupand vinyl group at the end of the molecule or as the side chain.

It is preferable that the silicone compound has a number-averagemolecular weight of 200 or greater and more preferably in the range of500 to 5,000,000. The form of the silicone compound may be any of oil,varnish, gum, powder and pellets.

(D) Stabilizer

As the stabilizer of component (D) which is added to the flame-retardantpolycarbonate resin composition of the present invention, where desired,at least one compound selected from the group consisting of antioxidantsand ultraviolet light absorbents is used.

As the antioxidant, phosphorus-based antioxidants and phenol-basedantioxidants are preferable. Examples of the phosphorus-basedantioxidant include triphenyl phosphite, diphenyl nonyl phosphite,tris(2,4-di-t-butyl) phosphite, trisnonylphenyl phosphite, diphenylisooctyl phosphite, 2,2′-methylenebis(4,6-di-t-butylphenyl) octylphosphite, diphenyl isodecyl phosphite, diphenyl mono(tridecyl)phosphite, 2,2′-ethylidenebis(4,6-di-t-butylphenol) fluorophosphite,phenyl diisodecyl phosphite, phenyl di(tridecyl) phosphite,tris(2-ethylhexyl) phosphite, tris(isodecyl) phosphite, tris(tridecyl)phosphite, dibutyl hydrogen-phosphite, trilauryl trithiophosphite,tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene diphosphonite,4,4′-isopropylidenediphenol dodecyl phosphite,4,4′-isopropylidenediphenol tridecyl phosphite,4,4′-isopropylidenediphenol tetradecyl phosphite,4,4′-isopropylidenediphenol pentadecyl phosphite,4,4′-butylidenebis(3-methyl-6-t-butylphenyl) ditridecyl phosphite,bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite,bis(2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite,bis(nonylphenyl) pentaerythritol diphosphite, distearyl pentaerythritoldiphosphite, phenyl bisphenol A pentaerythritol diphosphite,tetraphenyldipropylene glycol diphosphite,1,1,3-tris(2-methyl-4-di-tridecyl phosphite-5-t-butylphenyl)-butane and3,4,5,6-dibenzo-1,2-oxaphosphan-2-oxide.

Examples of the phenol-based antioxidant include hindered phenols suchas n-octadecyl 3-(3′,5′-di-t-butyl-4-hydroxyphenyl)propionate,2,6-di-t-butyl-4-hydroxymethylphenol and2,2′-methylenebis(4-methyl-6-t-butylphenol)pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate].

Examples of the ultraviolet light absorbent include benzotriazole-basedultraviolet light absorbents such as2-(2′-hydroxy-5′-methylphenyl)-benzotriazole,2-(2′-hydroxy-5′-t-butylphenyl)benzotriazole,2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-t-butylphenyl)-benzotriazole,2-(2′-hydroxy-3′,5′-diamylphenyl)benzotriazole,2-(2′-hydroxy-3′-dodecyl-5′-methylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-dicumylphenyl)benzotriazole and2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol];salicylate-based ultraviolet light absorbents such as phenyl salicylate,p-t-butylphenyl salicylate and p-octylphenyl salicylate;benzophenone-based ultraviolet light absorbents and triazine-basedultraviolet light absorbents.

As the stabilizer of component (D), compounds other than the aboveantioxidants and ultraviolet light absorbents such as radical scavengersand acid neutralizing agents can be used singly or in combination withthe antioxidants and the ultraviolet absorbents.

As for the contents of the components in the flame-retardantpolycarbonate resin composition of the present invention, the content ofthe polycarbonate resin of component (A) is in the range of 90 to 99.9%by mass. Since the composition comprises a relatively great amount ofcomponent (A), the excellent properties proper to the polycarbonateresin such as the excellent transparency, impact strength, heatresistance, electric properties and dimensional stability can beretained. The content of the aromatic vinyl resin having an acid saltgroup of component (B) is in the range of 0.05 to 5% by mass. Eventhough the composition comprises a relatively small amount of component(B), the practically sufficient flame-retarding property can be obtainedand, at the same time, the retention of the antistatic propertysufficient for preventing attachment of dusts to the surface of a moldedarticle can be provided when the flame-retardant polycarbonate resincomposition is molded into the article.

When the content of component (B) is smaller than 0.05% by mass, thepractically sufficient flame-retarding property cannot be obtained. Whenthe content of component (B) exceeds 5% by mass, the transparency andthe impact resistance decrease and the retention of the antistaticproperty is not provided sufficiently. It is preferable that the contentof the aromatic vinyl resin having an acid salt of component (B) is inthe range of 0.5 to 3% by mass. When the content of component (B) is inthis range, the retention of the antistatic property for preventingattachment of dusts to the surface of a molded article can be furtherimproved.

When the content of the silicone compound of component (C) having areactive group is in the range of 0.05 to 5% by mass, dropping of liquiddrops of the melted flame-retardant polycarbonate resin composition canbe suppressed. When the content of component (C) is smaller than 0.05%by mass, dropping of liquid drops of the melted flame-retardantpolycarbonate resin composition cannot be suppressed sufficiently. Whenthe content of component (C) exceeds 5% by mass, the transparency andthe impact resistance decrease.

The flame-retardant polycarbonate resin composition having excellentcolor tone and weatherability can be obtained by adding at least onestabilizer selected from antioxidants and ultraviolet light absorbentsas component (D) to the basic composition comprising components (A) to(C) described above. The content of the stabilizer of component (D) isin the range of 0.0001 to 1 part by mass and preferably in the range of0.001 to 0.5 parts by mass per 100 parts by mass of the total ofcomponents (A) to (C) as the basic components.

As for the process for producing the flame-retardant polycarbonate resincomposition of the present invention, components (A) to (C) describedabove in amounts corresponding to the contents described above and,where necessary, component (D) described above are suitably mixed andmelt kneaded. For the mixing and the kneading, the components arepreliminarily mixed by a ribbon blender or a drum tumbler and, then,melt kneaded by a conventional apparatus such as Banbury mixer, a singlescrew extruder, a twin screw extruder, a multi-screw extruder andcokneader. The temperature of the melt kneading can be suitably selectedin the range of 240 to 300° C. For molding the composition obtained bythe melt kneading into an article, it is preferable that the meltkneaded composition is extruded by an extruder and preferably by anextruder of the vent type into strands and pellets are formed by cuttingthe formed strands.

Various molded articles can be produced from the pellets of theflame-retardant polycarbonate resin composition thus obtained inaccordance with various molding processes such as the injection molding,the injection compression molding, the extrusion molding, the blowmolding and the press molding.

Since the molded article of the present invention obtained as describedabove exhibits the excellent flame-retarding property and retains theantistatic property to prevent attachment of dusts, the molded articlecan be advantageously used for applications to which these propertiesare required and applications to which transparency is required.Examples of the application to which the above properties are requiredinclude electric and electronic members such as housings and members ofcopiers, facsimile apparatuses, televisions, radios, tape recorders,video decks, personal computers, printers, telephones, informationterminals, refrigerators and electronic ranges. Examples of theapplications to which transparency is required include automobilemembers such as lenses of head lamps and members of lightingapparatuses.

The present invention will be described more specifically with referenceto examples in the following. However, the present invention is notlimited to the examples.

EXAMPLES 1 TO 8

[1] Preparation of a Flame-retardant Polycarbonate Resin Composition

Components (A) to (C) as the raw materials and component (D) as theadditive were used in amounts shown in Table 1 [the amounts ofcomponents (A) to (C) as % by mass and the amount of component (D) asthe part by mass per 100 parts by mass of the total of components (A) to(C)]. The components were supplied to a twin screw extruder of the venttype (manufactured by TOSHOBA KIKAI Co., Ltd.; TEM35) and melt kneadedat 280° C. After the resultant composition was extruded to form strands,the formed strands were cut and pellets of the flame-retardantpolycarbonate resin composition were obtained.

After the obtained pellets were dried at 120° C. for 12 hours, thepellets were molded in accordance with the injection molding at themolding temperature of 270° C. and a mold temperature of 80° C. andvarious test pieces were prepared.

As components (A) to (C) of the raw materials and component (D) of theadditive, the following substances were used.

(A) Polycarbonate Resin

(A-1) A polycarbonate resin having a structural unit derived from2,2-bis(4-hydroxyphenyl)propane, a linear structure, a viscosity-averagemolecular weight of 19,000 and a melt flow rate of 19 g/10 minutes asmeasured in accordance with the method of Japanese Industrial Standard K7210 under a load of 2160 g at a temperature of 280° C.

(A-2) A polycarbonate resin containing 4% by mass of a block having 30structural units derived from dimethylsiloxane and the remaining amountof a structural unit derived from 2,2-bis(4-hydroxyphenyl)propane andhaving a linear structure and a viscosity-average molecular weight of15,000.

(B) Aromatic Vinyl Resin Having an Acid Salt Group

(B-1) Sodium polystyrenesulfonate having a weight-average molecularweight of 20,000 and a fraction of sulfonation of 100%.

(B-2) Potassium polystyrenesulfonate having a weight-average molecularweight of 20,000 and a fraction of sulfonation of 40%.

(B-3) A 30% by mass aqueous solution of potassium polystyrenesulfonatehaving a weight-average molecular weight of 20,000 and a fraction ofsulfonation of 40%.

(C) Silicone Compound Having a Functional Group

(C-1) Methylphenylsilicone having a refractive index of 1.51 and vinylgroup and methoxyl group as the functional groups [manufactured bySHIN-ETSU CHEMICAL Co., Ltd.; KR219].

(C-2) Methylphenylsilicone having a refractive index of 1.49 andmethoxyl group as the functional group [manufactured by TORAY DOWCORNING Co., Ltd.; DC3037].

(D) Stabilizer

(D-1) Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate[manufactured by CIBA SPECIALTY Co., Ltd.; IFGNOX1076].

(D-2) Tris(2,4-di-t-butylphenyl) phosphite [manufactured by CIBASPECIALTY Co., Ltd.; IRGAFOS168].

(D-3) 2-(2H-Benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol[manufactured by CIBA SPECIALTY Co., Ltd.; TINUVIN329].

(D-4) 2-(4,6-Diphenyl-1,3,5-triazin-2-yl)-5-(hexyl)oxyphenol[manufactured by CIBA SPECIALTY Co., Ltd.; TINUVIN1577].

[2] Evaluation of the Flame-retardant Polycarbonate Resin Compositions

Using the test pieces of the flame-retardant polycarbonate resincompositions obtained in [1] described above, the following propertiesof the compositions were evaluated. The results are shown in Table 1.

(1) Izod Impact Strength

The Izod impact strength was measured in accordance with the method ofASTM D256 at 23° C. using a test piece having a thickness of 3.18 mm.

(2) Yellow Index

The yellow index was measured in accordance with the method of JapaneseIndustrial Standard K 7102 using a square plate having a size of 80×80mm and a thickness of 3 mm as the test piece and a tester manufacturedby NIPPON DENSHOKU KOGYO Co., Ltd.

(3) Haze

The haze was obtained from the transmittance of parallel light measuredin accordance with the method of Japanese Industrial Standard K 7105using a square plate having a size of 25×25 mm and a thickness of 3.2 mmas the test piece and a tester manufactured by NIPPON DENSHOKU KOGYOCo., Ltd.

(4) Half-life of Charged Voltage

Using a square plate having a size of 25×35 mm and a thickness of 3 mmas the test piece, the test piece was charged with electricity under anapplied voltage of 9 kv for 1 minute. The time (second) passed from thetime when the application of the voltage was stopped to the time whenthe electric potential reached a half of the initial electric potentialwas measured.

(5) Half-life of Charged Voltage After Washing with Water

The test piece used in (4) described above was washed with water at 23°C. for 1 minute and water attached to the test piece was wiped off. Thewashed test piece was charged with static electricity under an appliedvoltage of 9 kv for 1 minute. The time (second) passed from the timewhen the application of the voltage was stopped to the time when theelectric potential reached a half of the initial electric potential wasmeasured.

(6) Resistance to Light

On a black panel in a xenon weather meter [manufactured by ATLASCompany; CI65; the output: 6.5 kW], a test piece was exposed to thelight at 63° C. for 300 hours. The hue (L, a, b) of the exposed testpiece was measured by a color difference meter in accordance with themethod of Japanese Industrial Standard K 7103 and the change in the hue(ΔE) was obtained.

(7) Flame-retarding Property

A test piece having a thickness of 1.5 mm was subjected to the verticalburning test in accordance with the method of Underwriters LaboratorySubject 94.

(8) Oxygen Index

The oxygen index was obtained in accordance with the method of JapaneseIndustrial Standard K 7201.

Comparative Examples 1 to 8

[1] Preparation of a Flame-retardant Polycarbonate Resin Composition

Components (A) to (C) of the raw materials and Components (D) and (E) ofthe additives were used in amounts shown in Table 2 (the same as thosein Examples). The components were supplied to a twin screw extruder ofthe vent type (manufactured by TOSHOBA KIKAI Co., Ltd.; TEM35) and meltkneaded at 280° C. After the resultant composition was extruded to formstrands, the formed strands were cut and pellets of the flame-retardantpolycarbonate resin composition were obtained.

After the obtained pellets were dried at 120° C. for 12 hours, thepellets were molded in accordance with the injection molding at themolding temperature of 270° C. and a mold temperature of 80° C. and testpieces and molded articles were prepared.

As components (A) to (C) of the raw materials and components (D) and (E)of the additives, the following substances were used.

(A) Polycarbonate Resin

Polycarbonate resin (A-1) used in the Examples.

(B) Aromatic Vinyl Resin Having an Acid Salt Group

Aromatic vinyl resin having an acid salt group (B-2) used in theExamples and the following metal salts.

(B-4) Potassium perfluorobutanesulfonate [manufactured by DAINIPPON INKKAGAKU KOGYO Co., Ltd.; MEGAFAC F114]

(B-5) Sodium dodecylbenzenesulfonate [manufactured by TAKEMOTO YUSHICo., Ltd.; ELECUT S412-2]

(C) Silicone Compound Having a Functional Group

(C-3) Dimethylsilicone having no functional groups [manufactured byTORAY DOW CORNING Co., Ltd.; SH200]

(E) Other Components

(E-1) Polytetrafluoroethylene [manufactured by ASAHI GLASS Co., Ltd.;CD076]

[2] Evaluation of the Flame-retardant Polycarbonate Resin Compositions

Using the test pieces of the flame-retardant polycarbonate resincompositions obtained in [1] described above, the same properties of thecompositions as those of the compositions in Examples 1 to 8 wereevaluated. The results are shown in Table 2.

TABLE 1 Example 1 2 3 4 5 6 7 8 Composition A (A-1) 99.5 98.5 98.5 98.098.0 98.0 96.7 (A-2) 99.6 B (B-1) 0.2 0.1 (B-2) 1.0 1.0 1.0 1.0 1.0(B-3) 3.0 C (C-1) 0.3 0.5 0.5 0.5 0.5 0.3 (C-2) 0.5 0.3 D (D-1) 0.1 0.10.1 0.1 0.1 0.1 (D-2) 0.1 0.1 0.1 0.1 0.1 0.1 (D-3) 0.3 (D-4) 0.3 0.30.3 0.3 Evaluation Izod impact strength 85 80 85 80 85 80 85 85 (kJ/m²)Yellow index 10 5 2 3 3 5 2 6 Haze 7 4 2 2 2 5 2 5 Half-life of charged300 15 10 10 5 20 10 300 voltage (sec) Half-life of charged 280 15 10 105 20 10 300 voltage after washing with water (sec) Resistance to light12 15 10 6 4 4 3 3 Flame-retarding V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0property (UL 94) Flame-retarding 36 35 36 36 36 35 37 38 property(oxygen index)

TABLE 2 Comparative Example 1 2 3 4 5 6 7 8 Composition A (A-1) 99.099.5 93.5 93.0 98.5 98.5 98.5 98.5 B (B-2) 1.0 6.0 1.0 1.0 1.0 (B-4) 1.0(B-5) 1.0 C (C-1) 0.5 0.5 6.0 0.5 0.5 (C-3) 0.5 E (E-1) 0.5 D (D-1) 0.10.1 0.1 0.1 (D-2) 0.1 0.1 0.1 0.1 (D-3) (D-4) 0.3 0.3 0.3 0.3 EvaluationIzod impact strength 75 85 30 25 75 75 30 10 (kJ/m²) Yellow index  8  220 10 12 15 15 20 Haze 10  2 25 40 90 90 90 90 Half-life of charged 25very  5 10 30 30 very  3 voltage (sec) long long Half-life of charged 25very  5 10 30 30 very very voltage after washing long long long withwater (sec) Resistance to light 18  6 30 13  4  4  3 20 Flame-retardingV-2 V-2 V-2 V-2 V-2 V-0 V-2 V-2 property (UL 94) Flame-retarding 35 3031 34 33 35 34 27 property (oxygen index)

INDUSTRIAL APPLICABILITY

In accordance with the present invention, the flame-retardantpolycarbonate resin composition which exhibits the excellentflame-retarding property and retention of the antistatic property for along time to prevent the attachment of dusts and the molded articlethereof can be provided.

1. A flame-retardant polycarbonate resin composition, which comprises 90to 99.9% by mass of a polycarbonate resin as component (A), 0.05 to 5%by mass of an aromatic vinyl resin having an acid salt group ascomponent (B), and 0.05 to 5% by mass of a silicone compound having areactive group as component (C), wherein the refractive index of thesilicone compound is in the range of 1.45 to 1.55.
 2. A flame-retardantpolycarbonate resin composition according to claim 1, wherein thepolycarbonate resin of component (A) is a polycarbonate copolymer resinhaving a structural unit derived from an organosiloxane.
 3. Aflame-retardant polycarbonate resin composition according to claim 1,wherein the aromatic vinyl resin having an acid salt group of component(B) is a metal salt of a polystyrenesulfonic acid.
 4. A flame-retardantpolycarbonate resin composition according to claim 1, wherein thesilicone compound having a reactive group of component (C) is a siliconecompound having a reactive group and phenyl group.
 5. A flame-retardantpolycarbonate resin composition according to claim 1, which furthercomprises at least one stabilizer selected from a group consisting ofantioxidants and ultraviolet light absorbents as component (D).
 6. Amolded article prepared by molding a flame-retardant polycarbonate resincomposition described in claim
 1. 7. A molded article according to claim6, which is a member of an electric or electronic apparatus, a member ofan automobile or a member of a lighting apparatus.
 8. A molded articleaccording to claim 6, which is a lens of a head lamp of an automobile.9. A flame-retardant polycarbonate resin composition according to claim1, wherein the flame-retardant polycarbonate resin composition has ahaze in the range of 7 to 2.